Haptic technology is a tactile feedback technology which takes advantage of a user's sense of touch by applying forces, vibrations, and/or motions upon the user to convey information. In the past, tactile feedback has been used to assist in the creation and control of virtual objects (i.e. objects existing only in a computer simulation), and to enhance control of remote machines and devices.
More recently, however, haptic technology has been used in portable electronic devices to supplement visual content. For example, some devices use haptic technology to produce vibrations in response to touch. This may be combined with touch-sensitive screens, where the vibrations can be used to acknowledge selection of on-screen content by the user. In other devices, vibrations have been used to direct a user to a particular on-screen feature, and even to create a tactile representation of an image to enable perception of displayed content with reduced cognitive effort (as described in WO 2009/097866 A1).
Human skin uses four different mechanical receptors (mechanoreceptors) to detect pressure, vibrations and texture. These include the Meissner corpuscle, the Merkel disc, the Pacinian corpuscle, and the Ruffini ending. Known haptic devices typically stimulate these receptors using one or more of the following: pneumatic stimulation (jets of pressurised air), vibro-tactile stimulation (vibrating actuators), electrotactile stimulation (electric fields), and functional neuromuscular stimulation (electric currents).
The perception of surface texture is mediated by vibrations in the skin, which are encoded by Merkel discs, Meissner corpuscles and Pacinian corpuscles. In general, different textures give rise to different frequencies of vibration. Pacinian corpuscles can detect vibrations with frequencies of between 70 and 1000 Hz, but are especially susceptible to vibrations in the 200-400 Hz range (corresponding to the frequencies generated upon a finger tip by textures comprising features smaller than 200 μm when the finger is moved at a speed of 0.1 m/s). On the other hand, Meissner corpuscles have a higher sensitivity when sensing vibrations with a frequency of 10-50 Hz (corresponding to features of between 2 and 10 mm in size at a finger speed of 0.1 m/s). Similarly, Merkel discs can detect vibrational frequencies of 5-15 Hz (corresponding to a lengthscale of around 6-20 mm).
To enable the accurate detection of surface texture, it would be beneficial if haptic devices induced skin vibrations at frequencies most detectable by the specific mechanoreceptors. Many known haptic systems, however, do not stimulate mechanoreceptors selectively or precisely, and as a result, are less effective at conveying tactile information to the user.
The apparatus and associated methods disclosed herein may or may not address this issue.
The listing or discussion of a prior-published document or any background in this specification should not necessarily be taken as an acknowledgement that the document or background is part of the state of the art or is common general knowledge. One or more aspects/embodiments of the present disclosure may or may not address one or more of the background issues.